Erosion in mountain belts results from the complex interplay between tectonic and climatic forces. In order to assess how these forces interact to control orogenic erosion, it is essential to establish a detailed record of the long-term erosional history of mountain belts. The thermochronologic ages preserved in syn-orogenic sediments reflect cooling during exhumation of the source terrane and therefore detrital studies represent a powerful tool with which to establish a record of mountain erosion. Most investigations utilize a single thermochronometer to assess the cooling history preserved in a population of grains. However, the individual grains in a sediment or sedimentary rock do not necessarily share a common thermal history and were likely derived from different areas within a mountain belt that may erode at distinct rates. This exploratory, field-oriented study is focused on developing an alternative approach that uses paired thermochronologic ages from syn-orogenic conglomerate deposits. Because all grains in a single cobble share a common thermal history, paired dating reveals the detailed time-temperature path taken by the sample during exhumation. These thermal histories are used to constrain the erosional history of the source terrane. This approach is being tested in a small area of the Spanish Pyrenees, where the Sierra de Sis conglomerate body preserves a 20 million year history of syn-orogenic deposition. The cooling histories from several samples throughout the stratigraphic section are being measured to hypothesize how the rate of erosion in the mountain belt may have evolved throughout the lifespan of the orogen. To investigate how variations in the erosion rate may be associated with pulses of faulting, the thermochronologic results is also compared with new estimates on the timing of local thrusts obtained from the dating of fault gouge.
This research holds significant promise for enhancing earth scientists' understanding of the long-term evolution of mountains. A major question in contemporary tectonics is how tectonic and climatic forces interact to control the shape and structure of mountain belts. This exploratory study is seeking new tools to obtain the detailed and long-term records of erosion necessary to address this problem. Once established, this approach may be widely applied to reveal the erosional history of orogenic belts worldwide, including ancient settings where all that remains of a mountain belt are its eroded remnants. In addition, it will support an early career post-doctoral scientist.
